I'd recommend starting from the beginning. But if you don't want to do that pick up the manga around volume 10. That's when all the changes happen. If you want a specific chapter I'm afraid to say this: Use the search function.

better start from the beginning since there were a lot of explanations that were not shown in the anime. besides If you've already watched the anime you'd be completely confused on why Raki isn't with clare still up to date in the manga.